Built-In Safety Measures; Overcurrent Protection; Lightning Protection - Canon FAX L1000 Service Manual

FAX-L1000 Chapter 1: Safety and Precautions

4.3 Built-in Safety Measures

4.3.1 Overcurrent protection

This fax is provided with an overcurrent protection circuit with built-in current fuse and
thermal fuse, to prevent abnormal rises in temperature if an overcurrent flows to the motors
and power supply due to driver IC trouble, software lockup and short circuits.
Protected Parts
Document read motor
Stamp unit (option)
Power supply unit
Fixing heater

4.3.2 Lightning protection

This fax is provided with a function for protecting electronic components from abnormal
voltage caused by lightning.
Protected Parts
NCU board ass'y
Power supply unit
When protection is not possible
The NCU board sometimes may not be protected even by the protection
circuits if lightning strikes the telephone line.
NOTE
Safety Measures
IC protector (FU2) on SCNT board
Current fuse (FU1) on SCNT board
Glass-tube current fuse (F1 (125V, 15A), F2 (125V,
6.3A)), overcurrent protection circuit
Thermal fuse (446°F/230°C), thermistor
Safety Measures
Arrestors (AR1, AR2) located at the primary side
of the NCU board discharge a voltage of more than
DC 320 to 350V via the telephone line or the power
cord.
Surge-absorber (NR3) located at the primary side
of the power supply unit goes into short-mode at a
voltage of more than 423V, and breaks. After this,
the glass-tube current fuse F2 or F1 blows.
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